I like Presencia 3-ply, 60-weight all cotton thread for piecing and Presencia 3-ply, 50-weight all cotton thread for machine quilting. King Tut 40-weight all cotton and Sulky 30-weight all cotton are also good threads for machine quilting.
I use a size 70 needle with the 60-weight thread for piecing and a size 80 needle with the 50-weight.